Image forming devices including copiers, laser printers, facsimile machines, and the like, include a photo conductive drum (hereinafter “photoconductor”) having a rigid cylindrical surface that is coated along a defined length of its outer surface. The surface of the photoconductor is typically charged to a uniform electrical potential and then selectively exposed to light in a pattern corresponding to an original image. The areas of the photoconductive surface exposed to light are discharged, thus forming a latent electrostatic image on the photoconductive surface. A developer material, such as toner, having an electrical charge such that the toner is attracted to the photoconductive surface is used for forming the image. The toner is normally stored in a reservoir adjacent to the photoconductor and is transferred to the photoconductor by the developer roll. The thickness of the toner layer on the developer roll may be controlled by a nip, which is typically formed between a doctor blade and the developer roll. A recording sheet, such as a blank sheet of paper, may then be brought into contact with the discharged photoconductive surface and the toner therein is transferred to the recording sheet in the form of the latent electrostatic image. The recording sheet may then be heated thereby permanently fusing the toner to the sheet. In preparation for the next image forming cycle, the photoconductive surface may be discharged and residual toner removed.
FIGS. 1 and 2 illustrate typical toner housings. Developer roller 4, doctor blade 5, and toner reservoir 6 may be supported and held together by a toner cartridge housing 2. Housing 2 may be made of plastic, molded parts and may be configured to retain the internal components. In particular, housing 2 may support doctor blade 5 in, e.g., close contact with developer roller 4, and may provide a nip point that may apply a uniform layer of toner to the drum. Some toner housings 2 may also support a doctor blade spring 7 that may bias doctor blade 5 toward developer roller 4.
As shown in FIGS. 1 and 2, typical toner cartridge housings may also have a stop post 12 positioned above doctor blade 5 opposite developer roller 4. Stop post 12 may function to control the maximum movement of doctor blade 5 away from developer roller 4. Stop posts may function to ensure safety during handling of the cartridge 1, e.g., they may keep the doctor blade within the cartridge. By way of example, if the cartridge is dropped, the stop post may prevent the doctor blade from separating from the housing and possibly damaging the cartridge, image forming apparatus, or injuring a person handling the equipment.
Typical toner housings may also have a retention post 14 and a retention block 16. Retention posts 14 and retention blocks 16 may function to maintain doctor blade 5 in the proper orientation with the doctor blade lower edge positioned against developer roller 4. The post and block may work in combination and the doctor blade may contact only one or both during the toner transfer process. They may also function to effectively control the positioning of the doctor blade without causing friction with the doctor blade that may restrict the movement of the doctor blade to and from the developer roller. Stop posts, retention posts, and retention blocks may be constructed as a unitary piece having a common back section 18. (See FIG. 1).